1. Technical Field
The present application relates to offshore oil and gas drilling devices, and in particular, to a floating type self-lifting drilling platform.
2. Related Art
In the current trend of increasing energy demands in the world and gradually running out onshore oil and gas resources, exploring broader energy supply ways has become a key point of development all over the world. The offshore oil and gas exploration technology is developed especially rapid. The proportion of the total yield of the offshore oil and gas in the total yield of the oil and gas in the world has increased from 20% in 1997 to more than 40% in nowadays, where the yield of deep water oil and gas accounts for about more than 30% of the yield of the offshore oil and gas. Therefore, for three offshore drilling devices, including a self-lifting type drilling platform, a semi-submersible type drilling platform and a drilling ship, operation in deepwater is a main development tendency.
The self-lifting type drilling platforms account for more than 60% of the total number of offshore drilling devices, and dominate the offshore oil and gas development for more than a hundred years. However, the platforms have the current operation water depth not exceeding 150 meters, and mainly operate on continental shelves of the continents. The self-lifting type drilling platform is formed by an upper layer platform and several lifting pile legs. Before operation, the platform is towed to a well position through self-propulsion or by a towboat. After being positioned, a pile leg lifting device inserts pile shoes under the pile legs into the seabed for fixation, the upper layer platform is lifted to a certain height above the sea surface, and a cantilever tower is extended from a deck to conduct the drilling operation. The self-lifting type drilling platform has characteristics such as good stability, good flexibility, and the cost lower than that of the semi-submersible type drilling platform and the drilling ship. However, the operation during positioning or dislocation of the platform is complicated, and the platform is sensitive to the wave. Moreover, as the water depth is increased, the cost is increased significantly.
For the sea area having the water depth of more than 200 meters, the existing floating platforms have respective limits. In fact, there are a large amount of oil and gas resources to be developed in the water area of 200 meters to 500 meters. If a semi-submersible type drilling platform and a drilling ship are newly built for a new oil production region with the water depth of 200 to 500 meters, requirements on exploration technologies and constructions may be met, but the cost is huge, it may be overkill, and has a poor economical efficiency. On the other hand, the number of existing self-lifting type drilling platforms is large, but a lot of the platforms in service cannot be continuously used due to the service lives of pile legs and pile shoes, and there will be a large number of self-lifting type drilling platforms retire in future ten years. Therefore, how to modify the lower part structures of the platforms by using the existing mature technologies to prolong the service lives thereof and enable them to operate in the sea area with the water depth of exceeding 150 meters will be a great technical breakthrough. Moreover, a large market of offshore engineering device modification is formed in the shipbuilding industry, which has a considerable economic prospect.